Delta Air Lines provided a surprisingly strong outlook for the second half of the year, and the entire airline sector is taking off as a result. Shares of Southwest Airlines (LUV 7.35%) traded up 7% as of 11:30 a.m. ET following Delta's strong report. Demand trends appear strongThere is a lot of investor uncertainty heading into airline earnings season. Although results came in largely as expected three months ago, growing concerns about the impact of inflation and tariffs on consumers kept many investors o ...